1. Field of the Invention
The present invention relates to field programmable gate arrays and similar circuits, and to logic function modules for use therein. More particularly, the present invention relates to logic function modules and interconnect structures for use in field programmable gate arrays and other similar circuit applications.
2. The Prior Art
Programmable logic blocks which are capable of performing a selectable one of a plurality of user-selectable logic functions are known in the prior art. U.S. Pat. No. 4,910,417 to El Gamal et al., assigned to the same assignee as the present invention, U.S. Pat. No. 5,055,718 to Galbraith et al., assigned to the same assignee as the present invention and U.S. Pat. No. 4,453,096 to Le Can et al., disclose logic modules composed of multiplexers capable of performing a plurality of combinatorial logic functions.
Later multiplexer based logic function modules are disclosed in U.S. Pat. No. 5,396,127 to Chan et al. The multiplexer based logic function modules disclosed in Chan et al. provide additional features such as multiterm gating on the inputs of the multiplexers and sequential elements cascaded after the multiplexers.
While these logic function circuits provide a degree of flexibility to the designer of user-programmable logic arrays, there is always a need for improvement of functionality and performance of such circuits.